Multivariate optimization of an ultrasound-assisted extraction procedure for the determination of Cu, Fe, Mn, and Zn in plant samples by flame atomic absorption spectrometry.

In this work, a simple, easy, and fast ultrasound-assisted extraction procedure for the determination of Cu, Fe, Mn, and Zn in plant samples was developed. Sample preparation conditions were optimized in a multivariate manner using mixture design and Box-Behnken. The extraction conditions adequate to obtain the maximum response were 90% power, 10 minutes, 40 °C temperature, and using an extraction solution composed of HNO3 and HCl at a concentration of 0.5 and 1.1 mol L-1, respectively, for a volume of 10 mL and 250 mg of samples. Accuracy was verified from the analysis of a certified reference material (Apple leaves, NIST 1515) yielding recoveries between 89 and 98% for the procedure. Precision was evaluated in a repeatability study (n = 10), yielding RSDs less than 6.7%, and the limits of quantification (mg kg-1) were 0.95, 2.42, 1.31, and 1.18 for Cu, Fe, Mn, and Zn, respectively. The concentrations determined in the stem and leaf of the mangrove species varied according to the collection point and the tissue, being consistent with other studies. The proposed procedure was efficient and reliable for elemental determination in plant samples, with the advantages of low cost and reagent consumption besides short analysis time as a valid alternative to the conventional sample preparation procedure.

Artificial neural network employment for element determination in Mugil cephalus by ICP OES in Pontal Bay, Brazil.

Fish are important sources of protein, making them very significant in the human diet. Although the consumption of this food is beneficial for health, it is essential that the product does not contain inorganic components above the limits recommended by the current legislation. Therefore, a method for determination of elements in fish (Mugil cephalus) samples was optimized. A simplex centroid mixture design with restriction was applied for optimization of the acid digestion of samples in an open system under reflux in order to evaluate the best ratio between the reagents HNO3, H2O2 and H2O. The results indicated that more intense analyte signals were obtained when a mixture containing 3.6 mL of HNO3 (65% v/v), 0.4 mL of H2O2 (30% v/v) and 6.0 mL of H2O was used. The accuracy of the method was assessed with a CRM of oyster tissue (NIST 1566b). The method presented relative standard deviations (RSDs) of 3.54%; 3.82%; 4.81% and 3.50% for Zn, Fe, Cu and S, respectively. The detection limits were 0.002 mg kg-1 for Cu and Zn and 0.02 mg kg-1 for Fe and S. The proposed method was applied for the determination of Zn, Fe, Cu and S in fish samples. A Kohonen Self-Organizing Map (KSOM) with K-means implementation was applied to better delimit the boundary between groups and the spatial and temporal influence on how concentrations of the chemical elements were perceived. To verify the separation, the Davies-Bouldin and Silhouette indices were used, obtaining 0.5374 and 0.8541, respectively, indicating satisfactory separation.

Development of procedure for sample preparation of cashew nuts using mixture design and evaluation of nutrient profiles by Kohonen neural network.

A procedure using ICP OES for sample preparation for the determination of copper, iron and manganese in cashew nuts was developed. Constrained simplex-centroid design was applied in the optimization of the digestion in microwave oven procedure, and the results evaluated from topological maps of the Kohonen network. The best proportion evaluated for the digestion of the sample with HNO3, H2O2 and H2O was 10:45:45 (%). With optimized conditions, the detection limits were 0.63, 4.3 and 0.37 mg kg-1, and quantification 2.1, 14 and 1.2 mg kg-1 for Cu, Fe and Mg, respectively. The precision (% RSD) was 1.84, 2.31 and 2.73, for Cu, Fe and Mg, respectively. The procedure proposed had the accuracy confirmed using NIST 1568b (at 95% reliability) and was applied in the samples obtaining concentrations in the range of 10.7-19.4, 44.3-67.2 and 11.0-21.4 mg kg-1 for Cu, Fe and Mg, respectively.

Determination and Evaluation of Metallothionein and Metals in Mugil cephalus (Mullet) from Pontal Bay, Brazil.

To assess environmental contamination, studies have been increasingly carried out using biomarkers to diagnose the effects of toxic metal exposure, such as metallothionein (MT). In this context, the aims of the present study were to determine Cd, Cu, Ni and Pb concentrations, by ICP-MS, in liver samples from Mugil cephalus from the municipality of Ilhéus, located in North-Southeastern Brazil, in the state of Bahia, which has been increasingly suffering from anthropogenic pressure, and to quantify total MT in liver and gills. Among essential metals, copper (199.2 µg g-1) presented concentrations approximately 7 times higher than allowed by the World Health Organization (30 µg g-1). Liver samples showed higher concentrations than gills. Metallothionein concentrations indicate differential contamination along the study area. The first sampling showed higher induction of MT synthesis overall. Differences between liver and gill MT concentration trends were relatively minor, which may indicate the adequacy of analyzing gills in an environmental monitoring context.

Aproveitamento da semente da jaca para a obtenção de endoglucanase a partir de Aspergillus níger por fermentação em estado sólido / The use of jackfruit seed for obtainment of endoglucanases from Aspergillus níger for fermentation in solid state

A jaca é alimento consumido por brasileiros sob diferentes formas: in natura, doces, conservas, dentre outros. Os resíduos derivados (sementes) desses produtos são ricos em nutrientes tais como proteínas, fibras, sais minerais e ácidos graxos podendo ser utilizados em diferentes alimentos como componentes enriquecedores, minimizando a poluição ambiental. O presente trabalho teve como objetivo avaliar o efeito da variação do teor de água (40%, 50% e 60%), do tempo de fermentação (24h, 48h, 72h e 96h) e da temperatura (25 °C, 30 °C e 35 °C), na produção de endoglucanase do fungo Aspergillus niger por fermentação em estado sólido, utilizando semente de jaca como substrato. As fermentações ocorreram em estufa bacteriológica, a endoglucanase foi quantificada como carboximetilcelulase utilizando CMC como substrato e o teor de proteína solúvel foi determinado pelo método de Bradford. O melhor resultado, atividade específica de 138,45 (U/mg), foi obtido nas condições de fermentação realizada com 60% do teor de água a 35 °C no tempo de 72h. A partir dos resultados obtidos foi possível concluir que a temperatura de fermentação foi o principal fator que afetou a produção da CMCase pelo Aspergillus niger a partir do semente de jaca.

Jackfruit is a kind of food eaten by many Brazilians in different ways: fresh, sweets, conserves, among others. The residue (seeds) derived from these products is rich in nutrients such as proteins, fibers, mineral salts and fatty acids, and it can be used in different kinds of food as enriching compounds, minimizing environmental pollution. The present study aimed to evaluate the effect of water percentage variation (40, 50, and 60%), time of fermentation (24, 48, 72, and 96 hours), and temperature (25, 30, and 35ºC) in endoglucanases production for Aspergillus niger fungus, through fermentation in solid state, having jackfruit seed as substratum. The fermentations took place in bacteriological greenhouse; endoglucanases was quantified as carboximetil-cellulose using CMC as substratum, and the percentage of solvable protein was determined by Bradford method. The best result, specific activity 138,45 (U/mg), was obtained at the conditions of fermentation realized with 60% of water percentage, at 35ºC, in 72 hours. Departing from results, it was possible to conclude that the temperature of fermentation was the main coefficient to affect the production of CMCase by Aspergillus niger from jackfruit seed.